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Author: Subject: Way off topic - Central heating help
joneh

posted on 3/5/18 at 07:16 AM Reply With Quote
Way off topic - Central heating help

Morning

This is way off topic and I hope you don't mind me asking here.

My central heating is playing up. When the hot water only is on, the rads get hot. Its NOT the 3 way valve. I thought this and replaced it and have confirmed that it works fine. Feeling the radiators, they heat upstairs first with the flow reversed via the return pipe, the FLOW pipe to downstairs then gets hot, and then the lower rads heat up.

Here's a diagram with some arrows drawn on it, showing how I think the flow is working - the only thing I can't figure out is where the hot water is getting back out, or how it completes a "pumped" circuit. As I said it doesn't flow back through the 3 way valve.

Description
Description


I'm thinking:

a. Its piped wrong - the return for the hot water circuit tee's in before the radiators upstairs and then pushes hot around in reverse. I've only lived here a year and each radiator has a TRV, which we turned up during the cold snap. Explains why we're only noticing that now its getting warmer.

b. A non-return valve has given up somewhere in the circuit under the floor

c. The boiler heat exchanger is partially blocked causing pressure to build up and force water the wrong way. Although the boiler kettles on hot water only - its fine on central heating and stays on for 30 mins - it doesn't cycle.

d. Something else?

The boiler is a conventional boiler (Netaheat Profile 80e), with a header tank and hot water cylinder.

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nick205

posted on 3/5/18 at 09:09 AM Reply With Quote
No immediate answer to the problem, but...

Has it worked before and suddenly started playing up or have you only just moved in?

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roadrunner

posted on 3/5/18 at 09:11 AM Reply With Quote
I've had similar issues, but it was my diverter valve playing up.
I also had hot water pumping straight into my heating header tank. After various flushes I traced it to what I can only describe as a swirl pot 3 way connector. It was crudded up with crap from the rads.
The best thing I did was fit a Magni flow in line from the boiler. Every now and then I open it up to empty all the metal deposits floating around my system.

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joneh

posted on 3/5/18 at 09:44 AM Reply With Quote
I'm not sure if its always been like that or not as we adjusted the TRV's on each radiator when it got cold. They could have been all closed when it was warm and therefore not heating up.

The "swirl pot 3 port connector" is an air separator - or sometimes called a bean can. I don't have one on this system.

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chris

posted on 3/5/18 at 03:47 PM Reply With Quote
you say the three port valve is working but is it wired correctly
heating only a
hot water only b
heating and hot water c sometimes known as mid position

may have got the sequence wrong its been a while since i fitted one

all hail the combi boiler

[Edited on 3/5/18 by chris]

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joneh

posted on 3/5/18 at 04:01 PM Reply With Quote
quote:
Originally posted by chris
you say the three port valve is working but is it wired correctly
heating only a
hot water only b
heating and hot water c sometimes known as mid position

may have got the sequence wrong its been a while since i fitted one

all hail the combi boiler

[Edited on 3/5/18 by chris]


Yup it's wired correctly and not the valve.

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Stevie_P

posted on 3/5/18 at 04:21 PM Reply With Quote
It's no help to you but I had similar problems after I'd had the 3 port valve replaced to find that he'd plumbed it in the wrong way around!
He was very sheepish and apologetic when I pointed out his error.

Sorry can't be much help
Steve

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joneh

posted on 3/5/18 at 04:26 PM Reply With Quote
quote:
Originally posted by Stevie_P
It's no help to you but I had similar problems after I'd had the 3 port valve replaced to find that he'd plumbed it in the wrong way around!
He was very sheepish and apologetic when I pointed out his error.

Sorry can't be much help
Steve


Amazing! I think the same plumber fitted my last boiler...

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jacko

posted on 3/5/18 at 05:49 PM Reply With Quote
Before i replaced all my c/heating we had a very similar problem to you it turned out to be the hot water tank, the coil inside it had a hole in it and hot water was getting into the rads at least this is what i was told by a plumber mate
jacko

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joneh

posted on 3/5/18 at 07:08 PM Reply With Quote
quote:
Originally posted by jacko
Before i replaced all my c/heating we had a very similar problem to you it turned out to be the hot water tank, the coil inside it had a hole in it and hot water was getting into the rads at least this is what i was told by a plumber mate
jacko


Blimey. It's definitely not that. If there was a hole, my hot water would be minging. It wouldn't reach radiators.

Thanks for the suggestions. Will try some cleaner first, if that fails will pull up carpet...

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Angel Acevedo

posted on 4/5/18 at 12:00 AM Reply With Quote
For me is just a valve not closing fully.
Warm water rises....
Gets to radiators... Cools a little bit getting heavier in the process..
Sinks down to the boiler again.

At home, I have three valves per shower, hot, cold and the one that acts as on off to the showerhead.
If I close that one, but n ot the other two,
I wake up to a warm shower and increased gas consumption due to the boiler cycling on due to thermo siphon..
Hope this helps.
AA





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hkp57

posted on 4/5/18 at 05:55 AM Reply With Quote
From your drawing and description everything points to the three way, to 100% rule that out disconnect the line from the 3 way that goes to your radiators and cap it off.

Run the hot water and check.

With your system I would think there is a by-pass valve between the feed and return pipes on the boiler, this is designed to make sure the boiler has minimum required flow in all operating modes, sometimes these are automatic or manual, either way if it is faulty, blocked or not adjusted incorrectly it may be causing a back flow.





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joneh

posted on 4/5/18 at 07:05 AM Reply With Quote
quote:
Originally posted by hkp57
From your drawing and description everything points to the three way, to 100% rule that out disconnect the line from the 3 way that goes to your radiators and cap it off.

Run the hot water and check.

With your system I would think there is a by-pass valve between the feed and return pipes on the boiler, this is designed to make sure the boiler has minimum required flow in all operating modes, sometimes these are automatic or manual, either way if it is faulty, blocked or not adjusted incorrectly it may be causing a back flow.


Thanks, its definitely not the three way valve. There isn't a by-pass with this system as its an always open system.

I've ordered some cleaner - will run that through and drain it down next weekend. If that doesn't work - I'll start pulling carpet to see how it's been plumbed.

Angel - Sounds like you have some sort of Combi system - mines a bit more old school than that. No other valves on mine other than the three way.

[Edited on 4/5/18 by joneh]

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Schrodinger

posted on 4/5/18 at 08:24 AM Reply With Quote
Could it be your pump turned up too high and pumping round too high a pressure, this would normally show with water returning to the header tank but this may also be blocked/have reduced flow.





Keith

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Angel Acevedo

posted on 4/5/18 at 01:56 PM Reply With Quote
quote:
Originally posted by joneh
quote:
Originally posted by hkp57
...

Angel - Sounds like you have some sort of Combi system - mines a bit more old school than that. No other valves on mine other than the three way....

[Edited on 4/5/18 by joneh]


Mine is not a heating system.
Mine is just a small water heater that feeds my showers..
The problem is that when I leave aforementioned valve open, Hot water and Cold water System become a closed circuit and then hot water rises, gets cool, then sinks and completes the circuit continually.
This may be happenning with your plumbing.
In the process, you spend more fuel than you want...





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loggyboy

posted on 4/5/18 at 04:15 PM Reply With Quote
Its not the timer thats wired incorrectly is it? so the call for hot water is also calling for heating?






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joneh

posted on 4/5/18 at 07:45 PM Reply With Quote
quote:
Originally posted by loggyboy
Its not the timer thats wired incorrectly is it? so the call for hot water is also calling for heating?


I thought that but ruled it out. Everything seems to come on and off at the right times, and the valve flows the right way for each scenario. Ta.

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gremlin1234

posted on 21/6/18 at 06:39 PM Reply With Quote
radiators here have just been on
I think its due to the system running the pump daily to save it seizing over summer
I also think this can then trigger it to gravity cycle the water...

have now turned boiler temp down

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adam1985

posted on 21/6/18 at 07:04 PM Reply With Quote
Did you get this fixed?
Reverse circulation can cause this problem, is the cylinder T the last on the return to the boiler?
Has it always done this or is it a new problem

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